U.S. Pat. Nos. 3,216,160 to H. A. Best and 3,667,572 to C. E. Anderson disclose means for mounting a stair in level attitude on a pair of stringer beams sloping at varying angles to the horizontal.
Still other forms of tread supporting assemblies appear in the patent literature and are also obtainable in the market place.
Despite the availability of such devices, however, there is considerable room for improvement.